Power vehicle with adjustable velocity profiles

ABSTRACT

Embodiments of the present invention relate to powered vehicles (e.g., lawn mowers) and, more particularly, to a control system for use with such a vehicle. In one embodiment, the vehicle includes a power source such as an internal combustion engine and one or more drive control levers incrementally movable between a neutral position and a maximum velocity position. The system may also include a velocity profile control system having an adjustment member that permits altering a ratio between control lever movement and velocity of an associated drive member or wheel. Thus, the system may alter a maximum potential velocity of the vehicle while the drive control lever(s) are positioned in the maximum velocity position without varying an output level of the power source.

TECHNICAL FIELD

Embodiments of the present invention relate generally to power vehiclesand, more particularly, to a velocity profile control system forlimiting a potential maximum velocity of a power vehicle independent ofan output level (e.g., throttle setting) of the vehicle's power source.

BACKGROUND

Power vehicles for carrying out diverse tasks are known. For instance,power lawn mowers are well known for use in turf maintenance. Suchmowers may either be of the walk-behind or riding variety. One type ofriding lawn mower that has grown increasing popular in recent years forboth homeowners and professionals alike is the ridingzero-turning-radius (ZTR) mower. While embodiments of the presentinvention are directed to control systems for use with a wide variety ofriding or walk-behind vehicles, it will, for the sake of brevity, bedescribed with respect to a ZTR mower.

A ZTR mower may typically incorporate a power source (e.g., internalcombustion engine or electric motor) coupled to a continuously variable,e.g., hydraulic, drive system. The drive system may include left andright hydraulic motors coupled to left and right drive wheels,respectively. Power may be transmitted from the prime mover to the leftand right hydraulic motors, e.g., via one or more pumps, to drive theleft and right drive wheels independently. The rotational speed anddirection of each drive wheel may then be controlled by an associateddrive control lever or “stick” under the control of an operator. Bymanipulating the control levers independently, each drive wheel can beseparately driven forward or backwards at varying speeds. As a result,the mower may be propelled forwardly or in reverse. By powering onewheel in the forward direction and slowing, stopping, or powering theopposite wheel in the reverse direction, the mower can execute a turn.

Each drive control lever may typically be positioned at any locationbetween a neutral and a full forward (and generally a full reverse)position. A stop may define the full forward (and full reverse) positionof each control lever.

During mower operation, the operator may seek to place the controllevers in the full forward position as this position allows resting ofthe levers against the stop. This may offer the operator increasedcomfort, as well as reduce inadvertent lever movement as a result of,for example, traversal of undulating terrain. However, this full forwardposition may also result in a vehicle speed that is in excess of what isdesired for some mowing tasks, e.g., bagging or mowing tall grass.Further, operators that are new to the operation of ZTR mowers may wishto limit the maximum potential speed of the mower until they havefamiliarized themselves with mower operation.

To reduce maximum mower speed, the operator may back the control leversaway from the full forward position. However, this action prevents theoperator from resting the levers against the stops. Alternatively, theengine throttle may be reduced. While throttle reduction is effective atreducing maximum vehicle speed (e.g., the speed at the full forwardcontrol lever position), it also reduces output to attached implements.For example, throttle reduction may reduce the rotational speed of theblades of an attached cutting deck, potentially reducing the cuttingefficiently of the mower.

To address this issue, some mowers may provide a control lever travellimiter. The limiter may selectively restrict travel of each drivecontrol lever by selectively interposing an intermediate stop to limitcontrol lever movement to a position short of the full forward position.While the travel limiter may effectively limit the range of controllever movement, it does so by reducing lever travel, not leversensitivity. Moreover, such travel limiting devices may be timeconsuming to adjust, complicated to operate, and/or difficult to engagewithout shutting down the mower.

SUMMARY

The present invention may overcome these and other issues with prior artmowers by providing, in one embodiment, a self-propelled vehicle thatincludes a chassis; a drive train attached to the chassis and configuredto power a drive member also attached to the chassis; and a prime moverattached to the chassis and operatively coupled to the drive train. Alsoprovided is a control member attached, for movement about an axis, tothe chassis, wherein the control member is operable to independentlyvary an output of the drive member. The control member is movableincrementally between a first position corresponding to zero output ofthe drive member, and a second position corresponding to a maximumpotential output of the drive member. Also provided is a control linkincluding: a first end operatively coupled to the control member; and asecond end operatively coupled to the drive train. The vehicle alsoincludes an adjustment member movably coupled to the chassis and movablebetween a first and a second position. The adjustment member isconfigured to move the first end of the control link between: a firstlocation, wherein the first end of the control link is located at afirst distance from the axis; and a second location, wherein the firstend of the control link is located at a second distance from the axis,the second distance less than the first distance.

In another embodiment, a self-propelled vehicle is provided thatincludes: a chassis; first and second drive trains each operativelyattached to the chassis and configured to power first and second drivemembers, respectively; and a prime mover attached to the chassis andoperatively coupled to both the first and second drive trains. Alsoprovided are first and second control levers each pivotally attachedabout a pivot axis to the chassis and operable to independently vary anoutput of the first and second drive members, respectively. Each controllever is pivotable incrementally between a first position correspondingto zero output of its respective drive member, and a second positioncorresponding to a maximum potential forward output of its respectivedrive member. The vehicle also includes first and second control linkseach having: first ends coupled to the first and second control levers,respectively; and second ends operatively coupled to the first andsecond drive trains, respectively. The vehicle further includes avelocity adjustment member coupled to the chassis and movable between afirst and a second position. The velocity adjustment member isconfigured to move the first ends of the first and second control linksbetween: a first location, wherein the first ends are at a firstdistance from the pivot axis; and a second location, wherein the firstends are at a second distance from the pivot axis, the second distanceless than the first distance.

The above summary is not intended to describe each embodiment or everyimplementation of the present invention. Rather, a more completeunderstanding of the invention will become apparent and appreciated byreference to the following Detailed Description of Exemplary Embodimentsand claims in view of the accompanying figures of the drawing.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWING

Embodiments of the present invention will be further described withreference to the figures of the drawing, wherein:

FIG. 1 is a front perspective view of an exemplary vehicle, e.g., ridingZTR mower, incorporating a velocity profile control system (VPCS) inaccordance with one embodiment of the invention;

FIG. 2 is a partial rear perspective view of a portion of the VPCS ofFIG. 1 with various mower structure removed for visibility;

FIG. 3 is a partial perspective view of one side of the mower of FIG. 2,illustrating an adjustment member of the exemplary VPCS, the adjustmentmember and the VPCS shown in a first or maximum potential velocityposition;

FIG. 4 is a rear perspective view of the adjustment member of the VPCSof FIG. 3;

FIGS. 5A-5C illustrate a portion of the mower and VPCS of FIGS. 2-3 whenthe adjustment member/VPCS is in the first or maximum potential forwardvelocity position, wherein: FIG. 5A is a side elevation view; FIG. 5B isa front elevation view of the adjustment member; and FIG. 5C is asection view taken along line 5C-5C of FIG. 5A;

FIGS. 6A-6B illustrate the portion of the mower and VPCS of FIGS. 5A-5C,but with the adjustment member/VPCS shown in a second or reducedpotential forward velocity position, wherein: FIG. 6A is a sideelevation view; and FIG. 6B is a front elevation view of the adjustmentmember; and

FIG. 7 is an enlarged side elevation view of the VPCS illustratingmovement of a drive control member, e.g., lever, between a first orneutral position and a second or full forward position.

The figures are rendered primarily for clarity and, as a result, are notnecessarily drawn to scale. Moreover, certain structure (e.g., variouschassis portions/components, fasteners, bearings, cables, and hydrauliccomponents (including but not limited to: conduits; hoses; and fittings,etc.)) may be removed from some or all of the views to better illustrateaspects of the depicted embodiments, or where inclusion of suchstructure/components is not necessary to an understanding of the variousembodiments of the invention. The removal of such structure/components,however, is not to be interpreted as limiting the scope of the inventionin any way.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following detailed description of illustrative embodiments of theinvention, reference is made to the accompanying figures of the drawingwhich form a part hereof, and in which are shown, by way ofillustration, specific embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand structural changes may be made without departing from the scope ofthe instant invention.

Embodiments of the present invention are directed to power vehicleshaving a power source and, more particularly, to self-propelled vehiclesincluding a velocity profile control mechanism or system for changing amaximum potential velocity of the vehicle while output (e.g., throttlesetting) of the power source is maintained at a constant level.Accordingly, the maximum potential speed of the vehicle may be adjustedwithout adversely impacting power delivered to other vehicle subsystems.VPCS in accordance with embodiments of the instant invention may also beeasily manipulated by an operator without the need to step off the mowerand without the need for tools.

Unlike some systems that provide a travel limiter to restrict a maximumposition of a speed control input (e.g., a speed control lever) to alesser or intermediate position, embodiments of the present inventionmay provide velocity control systems that actually vary a ratio of input(control lever movement) to output (vehicle ground speed) for a fixedpower source output. Thus, unlike travel limiters, the full range ofcontrol lever movement remains available regardless of the setting ofthe velocity profile control mechanism.

While the general construction of the power vehicle is not necessarilycentral to an understanding of the invention (e.g., configurations otherthan those illustrated may be utilized without departing from the scopeof the invention), embodiments of an exemplary vehicle will now bebriefly described.

FIG. 1 illustrates a vehicle, e.g., ZTR mower 100, having a chassis 102supporting a power source or prime mover, e.g., internal combustionengine 104. A pair of transversely opposing, ground-engaging drivemembers, e.g., first and second drive wheels or drive wheel assemblies106 (only left drive wheel 106 a visible in FIG. 1, with right drivewheel being a mirror image), may be coupled for powered rotation toopposing sides of the chassis 102 to support and propel the mower 100relative to a ground surface 103. A pair of front swiveling castorwheels 108 a and 108 b may also be provided to support the front end ofthe mower 100 relative to the ground surface.

As used herein, relative terms such as “left,” “right,” “forward,”“aft,” “rearward,” “top,” “bottom,” “upper,” “lower,” “horizontal,”“vertical,” and the like are from the perspective of one operating themower 100 while the mower is in an operating configuration, e.g., whilethe mower 100 is positioned such that the wheels 106 and 108 rest uponthe generally horizontal ground surface 103 as shown in FIG. 1. Theseterms are used herein only to simplify the description, however, and notto limit the scope of the invention in any way.

Moreover, the suffixes “a” and “b” may be used throughout thisdescription to denote various left- and right-side parts/features,respectively. However, in most pertinent respects, the parts/featuresdenoted with “a” and “b” suffixes are substantially identical to, ormirror images of, one another. It is understood that, unless otherwisenoted, the description of an individual part/feature (e.g., part/featureidentified with an “a” suffix) also applies to the opposing part/feature(e.g., part/feature identified with a “b” suffix). Similarly, thedescription of a part/feature identified with no suffix may apply,unless noted otherwise, to both the corresponding left and rightpart/feature.

Each drive wheel 106 may be powered by a separate drive train, e.g.,hydraulic drive unit (see FIG. 5A), which is, in the illustratedembodiment, configured as an integrated hydrostatic transaxle (IHT) 105.Each IHT may include a pump and a hydrostatic motor integrated into asingle housing. Both left and right IHTs 105 may be attached (e.g.,bolted) to the chassis 102 and be operatively coupled to the engine 104(e.g., via a belt connecting a drive sheave of the engine to an inputsheave of the IHTs) for powering the drive wheels. While notillustrated, other drive trains, e.g., mechanical gear or pulley drivensystems, may also be utilized without departing from the scope of theinvention. Moreover, other power sources, e.g., one or more electricmotors, could be substituted in place of the engine 104.

Although the illustrated mower has the drive wheels 106 in the rear,this configuration is not limiting. For example, other embodiments mayreverse the location of the drive wheels, e.g., drive wheels in frontand castor (or steerable wheels) in the back. Moreover, otherconfigurations may use different wheel configurations altogether, e.g.,a tri-wheel configuration. Still further, while embodiments of theinvention are herein described with respect to riding ZTR lawn mowers(hereinafter generically referred to merely as a “mower”), those ofskill in the art will realize that the invention is equally applicableto other types of walk-behind, ride-behind (e.g., such as thoseutilizing sulkies), and conventional ride-on mowers, as well as to mostany other walk-behind, ride-behind, or ride-on power utility vehicle(e.g., aerator, snow blower, blower/vacuum, spreader, etc.).

A cutting deck 114 may be attached to a lower side of the chassis 102generally between the drive wheels 106 and the castor wheels 108 in whatis commonly referred to as a mid-mount configuration. The cutting deck114 may form a downwardly-opening enclosure that defines a cuttingchamber. The cutting chamber may enclose one or more rotatable cuttingblades (not shown) that are each attached to a spindle journalled forrotation to an upper surface of the cutting deck. The cutting blades maybe operatively powered, via the spindles, by the engine 104. Duringoperation, power is selectively delivered to the spindles of the cuttingdeck 114, whereby the blades rotate at a speed sufficient to sever grassand other vegetation as the mower travels over the ground surface 103.In some embodiments, the cutting deck 114 includes deck rollers oranti-scalp wheels 115 to assist with supporting the cutting deck 114relative to the ground surface.

The mower 100 may also include an operator seat 112 to accommodate theoperator during mower use. From the seat 112, the operator may haveaccess to various controls, e.g., engine throttle, deck engagement,engine ignition, etc. Operator directional/speed control members, e.g.,left and right drive control levers 110 a, 110 b (referred to hereinmerely as “control levers”), may also be provided to permit control ofmower speed and direction. Each control lever 110 may be pivotallycoupled to the chassis 102 for pivotal movement about an axis, e.g., atransverse pivot axis 116 (see FIG. 2). As a result, each lever 110 maypivot from a first or neutral position “A” (as shown in FIGS. 1 and 2)in a first direction 118 to a second or full forward position “B” (seeFIG. 7) corresponding to a maximum potential forward output or velocityof the respective drive wheel. Each control lever may also pivot aboutthe pivot axis 116 in a second direction 120 (see FIG. 2) to a third orfull reverse position (not shown) corresponding to a maximum potentialreverse output or velocity of the respective drive wheel. Duringoperation, each control lever may move incrementally in either direction118 or 120 to any position between the neutral position and the fullforward position (as well as the full reverse position).

Each control lever may also pivot about a second or longitudinal axis117 (the axis 117 being parallel to a longitudinal axis 101 of the mower100 as shown in FIG. 2). Pivoting about the axis 117 may improve ingressto/egress from the seat 112.

As depicted in FIG. 2, as each lever 110 pivots about the axis 116, itmay impart translational movement to a first end of a connected controllink, e.g., tie rod 122, as further described below. A second end ofeach tie rod 122 may attach to a pump input arm 124 (see FIG. 5A) of thecorresponding IHT 105. The position of the pump input arm 124 maycontrol IHT output, i.e., the rotational speed and direction of thehydrostatic motor and thus its associated drive wheel 106. The tie rod122 may include rod end connections at one or both of the first andsecond ends to permit out-of-plane travel.

As one can appreciate, incremental movement of either lever 110 aboutthe axis 116 in the direction 118 may cause corresponding incrementalmovement of the associated tie rod 122 in a first (e.g., rearward)direction, which may (via displacement of the associated pump input arm124) produce corresponding rotational output of the respective IHT 105and drive wheel 106 in the forward travel direction. Similarly,incremental movement of either lever 110 about the axis 116 in thesecond direction 120 may cause corresponding incremental movement of theassociated tie rod 122 in a second (e.g., forward) direction, which mayproduce rotational output of the respective IHT 105 and drive wheel 106in the reverse travel direction. The degree to which the levers 110 arepivoted may control the rotational speed of the respective drive wheels106. As those of skill in the art may appreciate, powering one drivewheel 106 in the forward direction and slowing, stopping, or poweringthe opposite drive wheel in the reverse direction, will allow the mowerto change direction.

While described herein as using a twin lever control system, it is to beunderstood that this configuration is not limiting as embodiments of thepresent invention may find application to vehicles having other, e.g.,single, control lever configurations or to configurations using othertypes of control members, e.g., steering wheels. Moreover, while theinvention is herein described with respect to a control system foraltering velocity, those of skill in the art will realize thatembodiments of the invention are equally applicable to systems adaptedto control other vehicle parameters.

With this introduction, an exemplary VPCS 200 will now be described withreference primarily to FIGS. 3-7. As stated elsewhere herein, the VPCS200 may, for a fixed engine throttle setting and position of the drivecontrol lever 110, alter an output of the respective IHT 105 and thusthe speed of the associated drive wheel 106. Stated alternatively, theVPCS 200 may provide two different potential maximum vehicle speedscorresponding to the control levers 110 being in the full forwardposition B (see FIG. 7) even though engine speed remains constant. VPCSsin accordance with embodiments of the present invention may achieve thisvariation without the use of adjustable control lever stops or the like.As a result, the control levers may be movable through the same arc ofrotation regardless of the setting of the VPCS. In one embodiment, theVPCS 200 provides two different velocity settings. However, embodimentswherein the VPCS provides more than two settings are certainly possiblewithout departing from the scope of the invention.

FIG. 3 is an enlarged perspective view of one side of the mower 100 withvarious structure removed to better illustrate the drive control lever110 a, the VPCS 200, and related structure. As shown in this view, eachcontrol lever 110 may include an arm 126. The arm 126 may attach to abellcrank 202 with a bolt or pin 130, the latter defining thelongitudinal pivot axis 117. While shown as separate components, thecontrol lever 110 may, as used herein, refer to an assembly thatincludes not only the control lever 110, but also either or both of thearm 126 and the bellcrank 202.

The bellcrank 202, which may be part of the VPCS, may form a generallyL-shaped member that is pivotally attached to the chassis 102, via afastener or pin 204, such that the bellcrank may pivot about the pivotaxis 116. A first arm 206 of the bellcrank 202 may operatively connectto the first end 128 of the tie rod 122. In the illustrated embodiment,the control lever, e.g., the first arm 206, may define an elongate slot208 that captively receives a pin 130 attached to or otherwiseassociated with the first end 128 of the tie rod 122.

The control lever, e.g., bellcrank 202, may also include a second arm210 that, in the illustrated embodiment, extends rearwardly away fromthe pivot axis 116. The second arm 210 may pivotally attach to a firstend 132 of a damper 134 that has its second end 136 pivotally attachedto the chassis 102 (see e.g., FIG. 5A). The damper 134 may dampenmovement of the bellcrank 202, and thus the control lever 110, duringmower operation, e.g., to reduce inadvertent, abrupt lever movements.

As shown in FIG. 3, movement of the control lever 110 in the firstdirection 118 towards the second or full forward position B (see FIG. 7)causes the bellcrank 202 to pivot in the same direction about the pivotaxis 116 (the second position B of the control lever 110 correspondingto the maximum potential output of the respective drive wheel). As thebellcrank 202 pivots in the direction 118, the first arm 206 of thebellcrank moves generally rearwardly, causing the tie rod 122 to alsomove rearwardly and displace the pump input arm 124 of the IHT 105 (seeFIG. 5A). Conversely, movement of the control lever 110 in the seconddirection 120 results in displacement of the pump input arm 124 in theopposite direction.

The VPCS 200 may further include an adjustment member 220 that isillustrated separately in FIG. 4. The adjustment member 220 may, in oneembodiment, include a pivot rod 222 extending transversely to thelongitudinal axis of the vehicle (see FIG. 3). The pivot rod 222 of theadjustment member 220 may be journalled to the chassis 102 as indicatedby journal connections 232 shown in FIG. 3. As a result, the adjustmentmember may pivot about a pivot axis 223 defined by the pivot rod.

A forked portion or member 224 that forms an opening, e.g., elongateslot 225, may be positioned at each end of the pivot rod 222 andprotrude perpendicular to the axis 223. In the illustrated embodiment,the elongate slots 225 of the forked members 224 are aligned (i.e., areparallel) with one another (relative to the pivot rod 222). The forkedmembers 224, e.g., the elongate slots 225, may be configured to receiveand capture the first ends 128 of the tie rods 122 as further describedbelow.

The adjustment member 220 may further include a handle lever 226 fixedto the pivot rod and located, in one embodiment, between the two forkedmembers 224. In the illustrated embodiment, the handle lever 226 and thetwo forked members 224 are fixed (e.g., welded, staked, etc.) relativeto the pivot rod 222 to form a unitary member. The handle lever mayprotrude outwardly through a shaped cutout 228 formed in a portion,e.g., a sheet metal cover, of the chassis 102 as shown in FIG. 3. Theshaped cutout 228 may define at least two detents or ledges, eachconfigured to hold the handle lever 226 at a particular location withinthe cutout 228. In the illustrated embodiment, a first ledge 227 isformed by a lower surface of the cutout 228 itself, while a second ledge229 is formed by a protrusion extending into the cutout. As a result,the adjustment member, e.g., handle lever 226, may be movable between afirst position corresponding to the handle lever being seated betweenthe first ledge 227 and an overhang 231 (see FIG. 5B) in the cutout, anda second position corresponding to the handle lever being seated againstthe second ledge 229. A gripping head 230 (shown only in FIG. 3) may beattached to the outer end of the handle lever 226 to facilitate graspingby the operator.

FIGS. 5A illustrates a partial side elevation view of the VPCS 200 ofthe mower 100 with, once again, various mower structure removed forvisibility. In this view, the adjustment member 220/handle lever 226(and thus the VPCS) is shown in the first position as also illustratedin FIGS. 3 and 5B, and the control lever 110 is shown in the first orneutral position A (corresponding to zero output/velocity of therespective drive wheel).

With reference to FIG. 5C, the pin 130 may be pressed into the first end128 of the tie rod 122 such that it extends into not only the slot 208as shown in FIG. 3, but also protrudes from an opposite side of the tierod a sufficient distance to permit engagement with the slot 225 (seeFIG. 4) of the forked member 224. Thus, the adjustment member 220 may,as the handle lever 226 moves between the first and second positions,reposition the pin 130, and thus the first end of the tie rod 122,within the slot 208 of the bellcrank 202. FIG. 5A illustrates thelocation of the pin 130 within the slot 208 when the adjustment member220/handle lever 226 is in the first position (see also FIG. 5B), whileFIG. 6A illustrates the location of the pin 130 within the slot 208 whenthe adjustment member 220/handle lever 226 is in the second position(see also FIG. 6B illustrating the handle lever 226 resting upon thesecond ledge 229 corresponding to the second position of the handlelever).

FIG. 7 illustrates an enlarged view of the VCPS 200 and relatedcomponents/structure. In this view, the control lever 110 is shown inboth the first or neutral A position, and the second or fully engaged Bposition. Moreover, the adjustment member 220 and handle lever 226 areshown in both the first position (broken lines) and the second position.

As shown in FIG. 7, when the adjustment member 220 and handle lever 226are in the first position, the forked member 224 places the pin 130 ofthe tie rod 122 at a first location being at a first distance 233 (e.g.,radial distance) from the pivot axis 116. As a result, movement of thecontrol lever 110 between the A and B positions results in movement ofthe pin 130 over a first distance 234 as indicated in FIG. 7.

However, when the adjustment member 220 and handle lever 226 are in thesecond position (solid lines in FIG. 7), the forked member 224 placesthe pin 130 of the tie rod 122 at a second location being at a seconddistance 236 (e.g., radial distance) from the axis 116 that is less thanthe first distance 233. As a result, movement of the control lever 110between the A and B positions results in movement of the pin 130 over asecond distance 238 that is less than the first distance 234.

When the handle lever 226 is secured in either the first or secondpositions (e.g., when the handle lever 226 is biased against either theoverhang 231 or the second ledge 229 (see, e.g., FIG. 5B),respectively), the pin 130 may be pushed or preloaded against one of theends of the slot 208. This preload may result in torsion generated inthe pivot rod 222. This torsional preload may assist with maintainingthe VPCS 200, e.g., the handle lever 226 of the adjustment member 220,in the intended position during mower operation.

In the illustrated example, the control levers 110 may pivot about 15degrees between the A and B positions. When the adjustment member 220 isin the first position, movement of either control lever 110 from the Aposition to the B position will vary the respective drive wheel outputor speed from zero miles/hour (mph) to a potential maximum output ofabout 7 mph, yielding a control lever resolution of about 0.4 to about0.5 (e.g., about 0.47) mph per degree of lever movement. However, whenthe adjustment member 220 is in the second position, movement of eithercontrol lever 110 from the A position to the B position will vary therespective drive wheel speed from zero miles/hour (mph) to a potentialmaximum output of about 4 mph, yielding a control lever resolution ofabout 0.2 to about 0.3 (e.g., about 0.27) mph per degree of levermovement. As a result, the movement of the adjustment member may notonly alter the maximum potential speed of the mower 100 (at a constantengine throttle setting), but it may also alter the resolution of thecontrol levers.

While described herein with a particular control lever travel range,such a configuration is presented merely as an exemplary range for a ZTRmower such as that illustrated herein. Other embodiments providing moreor less travel to accommodate specific functionality are certainlypossible. Similarly, the various speed ranges described herein are alsoexemplary and not intended to limit the scope of the invention.

Embodiments of the present invention may thus permit operatormanipulation of the potential maximum speed of a vehicle, for a maximumspeed control input (e.g., control lever motion), without altering theoutput level of the vehicle power source. As a result, the operator mayalter the maximum potential velocity of the vehicle (the speedcorresponding to when the speed control input is in a maximum velocityposition) without altering the power delivery to other vehiclesubsystems. Thus, like a control lever travel limiter, embodiments ofthe present invention may provide a technique to limit maximum vehiclevelocity while the control levers are against a forward stop. However,unlike travel limiters, embodiments of the present invention permitfull, unrestricted travel of the control levers regardless of thevelocity adjustment member setting.

Illustrative embodiments of this invention are discussed and referencehas been made to possible variations within the scope of this invention.These and other variations, combinations, and modifications in theinvention will be apparent to those skilled in the art without departingfrom the scope of the invention, and it should be understood that thisinvention is not limited to the illustrative embodiments set forthherein. Accordingly, the invention is to be limited only by the claimsprovided below and equivalents thereof.

What is claimed is:
 1. A self-propelled vehicle comprising: a chassis; adrive train attached to the chassis and configured to power a drivemember also attached to the chassis; a prime mover attached to thechassis and operatively coupled to the drive train; a control memberattached, for movement about an axis, to the chassis and operable toindependently vary an output of the drive member, the control membermovable incrementally between a first position corresponding to zerooutput of the drive member, and a second position corresponding to amaximum potential output of the drive member; a control link comprising:a first end operatively coupled to the control member; and a second endoperatively coupled to the drive train; and an adjustment member movablycoupled to the chassis and movable between a first and a secondposition, the adjustment member configured to move the first end of thecontrol link between: a first location, wherein the first end of thecontrol link is located at a first distance from the axis; and a secondlocation, wherein the first end of the control link is located at asecond distance from the axis, the second distance less than the firstdistance.
 2. The vehicle of claim 1, wherein the drive train comprisesone or more hydrostatic transaxles.
 3. The vehicle of claim 1, whereinthe drive member comprises a ground-engaging drive wheel.
 4. The vehicleof claim 1, further comprising a cutting deck attached to the chassis.5. The vehicle of claim 1, wherein the adjustment member is pivotallyattached to the chassis and further comprises a forked portion definingan elongate slot configured to receive the first end of the controllink.
 6. A self-propelled vehicle comprising: a chassis; first andsecond drive trains each operatively attached to the chassis andconfigured to power first and second drive members, respectively; aprime mover attached to the chassis and operatively coupled to both thefirst and second drive trains; first and second control levers eachpivotally attached about a pivot axis to the chassis and operable toindependently vary an output of the first and second drive members,respectively, each control lever pivotable incrementally between a firstposition corresponding to zero output of its respective drive member,and a second position corresponding to a maximum potential forwardoutput of its respective drive member; first and second control linkseach comprising: first ends coupled to the first and second controllevers, respectively; and second ends operatively coupled to the firstand second drive trains, respectively; and a velocity adjustment membercoupled to the chassis and movable between a first and a secondposition, the velocity adjustment member configured to move the firstends of the first and second control links between: a first location,wherein the first ends are at a first distance from the pivot axis; anda second location, wherein the first ends are at a second distance fromthe pivot axis, the second distance less than the first distance.
 7. Thevehicle of claim 6, wherein the pivot axis extends transversely to alongitudinal axis of the vehicle.
 8. The vehicle of claim 6, furthercomprising a damper attached between the chassis and one or both of thefirst and second control levers.
 9. The vehicle of claim 6, wherein thefirst and second drive trains each comprise a hydrostatic transaxle. 10.The vehicle of claim 6, wherein the first and second drive memberscomprise ground-engaging drive wheel assemblies.
 11. The vehicle ofclaim 6, wherein the vehicle further includes a cutting deck attached tothe chassis.
 12. The vehicle of claim 6, wherein the adjustment membercomprises a pivot rod and a forked member fixed to ends of the pivotrod.
 13. The vehicle of claim 12, wherein the adjustment member furthercomprises a handle lever fixed to the pivot rod and configured tomanipulate the adjustment member between the first and second positions.14. The vehicle of claim 12, wherein each forked member defines anelongate slot configured to receive the first end of one of the controllinks.
 15. The vehicle of claim 6, wherein the first and second controllevers each define an elongate slot configured to receive the first endof the first and second control links, respectively.
 16. The vehicle ofclaim 6, wherein each of the first and second control levers are furtherpivotable about the pivot axis to a third position corresponding to amaximum reverse output of its respective drive member.
 17. Adifferentially steerable, self-propelled vehicle comprising: a chassis;first and second hydraulic drive units attached to the chassis andconfigured to power first and second drive wheels, respectively; a primemover attached to the chassis and operatively coupled to both the firstand second hydraulic drive units; first and second control leverspivotally attached about a pivot axis to the chassis and operable toindependently vary a velocity of the first and second drive wheels,respectively, each control lever pivotable incrementally between a firstposition corresponding to zero velocity of its respective drive wheel,and a second position corresponding to a maximum potential velocity ofits respective drive wheel; first and second tie rods each comprising: afirst end coupled to the first and second control levers, respectively;and a second end operatively coupled to the first and second hydraulicdrive units, respectively; and a velocity adjustment member pivotallycoupled to the chassis and pivotable between a first and a secondposition, the velocity adjustment member configured to move the firstends of the first and second tie rods between: a first location, whereinthe first ends are at a first distance from the pivot axis; and a secondlocation, wherein the first ends are at a second distance from the pivotaxis, the second distance less than the first distance.
 18. The vehicleof claim 17, wherein the adjustment member comprises a pivot rodextending transversely to a longitudinal axis of the vehicle, and firstand second forked members fixed to ends of the pivot rod and protrudingperpendicular to an axis of the pivot rod.
 19. The vehicle of claim 18,wherein the first and second forked members each define a slot thatreceives therein a pin fixed to the first end of the first and secondtie rods, respectively.
 20. The vehicle of claim 17, wherein each of thefirst and second control levers comprises first and second bellcranks,respectively, the first and second bellcranks each defining a slot thatreceives therein a pin fixed to the first end of the first and secondtie rods, respectively.